# Codex4 - For Serious Study — For serious language learners

> Vocabulary builder with spaced repetition and real-world usage focus. (iPhone/iPad app by Jonas Richner.)

- Source: https://appshunter.io/ios/app/codex4-for-serious-study/id6743228019 (this page in markdown: same URL + `.md`)
- Developer: [Jonas Richner](https://appshunter.io/developer/1801973188)
- Category: Education
- Price: Free with in-app purchases
- Rating: 5.00/5 from 2 App Store ratings · 2 written reviews indexed
- Age rating: 4+
- Requires: iOS 15.6 · 52 MB
- Languages: American English
- Released: 2025-05-29
- Data updated: 2026-08-21
- Monetization: freemium
- User reviews in markdown: https://appshunter.io/ios/app/codex4-for-serious-study/id6743228019/reviews.md

## What is Codex4?

Get fluent faster by learning the words you actually use.

Codex4 helps you build a usable vocabulary and keep it for the long term.

- Learn what you need: Add your own words from any text in one tap. Build vocabulary for your job, studies, or hobbies.
- Retain more with less effort: Reviews are timed by FSRS (a modern spaced-repetition model) so you study exactly when it counts.
- Master real usage: The app treats each word as a lemma, so forms and conjugations are covered naturally as you progress.
- Stay organized and motivated: Clear stats show what’s due, what’s known, and what’s next.
- Bring any content: Automatic word extraction and a context-aware lemmatizer handle homonyms and multi-word phrases.
- Your data stays yours: Keep access to review even after unsubscribing, and export your words and learning data anytime.

- No gimmicks: Fast sessions, clean design, built for serious learners.

Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

## Key features

- Add custom words from any text
- Spaced repetition reviews (FSRS)
- Master word lemmas and conjugations
- Clear progress statistics
- Automatic word extraction
- Data export and offline access

## Pricing and in-app purchases

Base price: Free.

**Subscriptions**

| Subscription | Price | Period |
| --- | --- | --- |
| Basic Yearly | $69.99 | per year |
| Pro Yearly | $85.00 | per year |
| Pro | $14.00 | per month |
| Basic | $12.99 | per month |


## Recent user reviews (2 of 2)

All indexed reviews: https://appshunter.io/ios/app/codex4-for-serious-study/id6743228019/reviews.md

### 1/5 — Not good

*2026-03-12*

Voice Problem

### 5/5 — The best language learning app ever! I've tried them all.

*2025-09-15*

So many apps do nothing to further language learning. This one does everything right. I started with zero knowledge and the way it shows you words in sentence format is priceless. You learn words in context and they stick. Flash cards never worked for me, EVER. This is GOLD and highly recommended.

## Frequently asked questions about Codex4

### What is Codex4's learning methodology?

Codex4 uses FSRS, a modern spaced-repetition model, to time reviews precisely when you need them. This ensures efficient learning and long-term retention of vocabulary.

### How does Codex4 handle word forms and conjugations?

The app treats each word as a lemma, meaning it naturally covers different forms and conjugations as you progress. This helps you master the real usage of words.

### Can I add my own words to Codex4?

Yes, you can add your own words from any text in one tap. This allows you to build a vocabulary tailored to your specific job, studies, or hobbies.

### What are the subscription options for Codex4?

Codex4 offers Basic and Pro plans, available monthly or yearly. Yearly plans include free trial periods of 7 days for Basic and 3 days for Pro.

### Does Codex4 have ads?

No, Codex4 does not contain advertisements. It is designed with a clean interface for serious learners, focusing on efficient study without distractions.

### Can I access my data if I unsubscribe from Codex4?

Yes, your data stays yours. You will retain access to your review progress even after unsubscribing, and you can export your words and learning data at any time.

### What devices does Codex4 support?

Codex4 is currently supported on iPhone and iPod devices. It is designed for mobile learning on the go.

### How often is Codex4 updated?

The latest version of Codex4 is 3.66, last updated on April 14, 2026. Updates ensure the app remains reliable and incorporates improvements for serious learners.

## Version history (last 5 releases)

### 3.66 — 2026-04-14

Bug fixes and performance improvements.

### 3.64 — 2026-03-31

Bug fixes and performance improvements.

### 3.62 — 2026-03-28

Bug fixes and performance improvements.

### 3.52 — 2026-03-24

Bug fixes and performance improvements.

### 3.49 — 2026-03-23

Bug fixes and performance improvements.

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## Related topics

[codex4](https://appshunter.io/ios/topics/codex4)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-21.*